Slow reboots due to ZFS cleanup in kern_shutdown() .. zio_fini()

[Peter Eriksson]

It’s a fairly standard Dell PowerEdge R730xd server with Intel Xeon E5-2620v4 CPUs & 256GB of RAM… (and an LSI SAS3 HBA and Intel 10GE ethernet)

CPU: Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz (2100.04-MHz K8-class CPU)
  Origin="GenuineIntel"  Id=0x406f1  Family=0x6  Model=0x4f  Stepping=1
  Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
  Features2=0x7ffefbff<SSE3,PCLMULQDQ,DTES64,MON,DS_CPL,VMX,SMX,EST,TM2,SSSE3,SDBG,FMA,CX16,xTPR,PDCM,PCID,DCA,SSE4.1,SSE4.2,x2APIC,MOVBE,POPCNT,TSCDLT,AESNI,XSAVE,OSXSAVE,AVX,F16C,RDRAND>
  AMD Features=0x2c100800<SYSCALL,NX,Page1GB,RDTSCP,LM>
  AMD Features2=0x121<LAHF,ABM,Prefetch>
  Structured Extended Features=0x21cbfbb<FSGSBASE,TSCADJ,BMI1,HLE,AVX2,SMEP,BMI2,ERMS,INVPCID,RTM,PQM,NFPUSG,PQE,RDSEED,ADX,SMAP,PROCTRACE>
  Structured Extended Features3=0x9c000400<MD_CLEAR,IBPB,STIBP,L1DFL,SSBD>
  XSAVE Features=0x1<XSAVEOPT>
  VT-x: PAT,HLT,MTF,PAUSE,EPT,UG,VPID,VID,PostIntr
  TSC: P-state invariant, performance statistics
real memory  = 274869518336 (262136 MB)
avail memory = 267244859392 (254864 MB)
Event timer "LAPIC" quality 600
ACPI APIC Table: <DELL   PE_SC3  >
FreeBSD/SMP: Multiprocessor System Detected: 32 CPUs
FreeBSD/SMP: 2 package(s) x 8 core(s) x 2 hardware threads

- Peter

>> 
>> uma_destroy() frees all of the memory cached in the zone back to the
>> page allocator.  This operation takes time proportional to the number of
>> cached items.  I would expect most of the time to be spent in
>> zone_reclaim(), called by zone_dtor().
> 
> But spending *minutes* there is really unexpected.
> I have never seen anything like that.
> I wonder if there is anything untypical about the system's hardware (like a very
> big number of processors) or configuration.
> 
> -- 
> Andriy Gapon